fix: LLMResultChunk cause concatenate str and list exception (#18852)

api/core/model_runtime/model_providers/__base/large_language_model.py

@@ -2,7 +2,7 @@ import logging
 import time
 import uuid
 from collections.abc import Generator, Sequence
-from typing import Optional, Union
+from typing import Optional, Union, cast
 
 from pydantic import ConfigDict
 
@@ -20,6 +20,7 @@ from core.model_runtime.entities.model_entities import (
     PriceType,
 )
 from core.model_runtime.model_providers.__base.ai_model import AIModel
+from core.model_runtime.utils.helper import convert_llm_result_chunk_to_str
 from core.plugin.manager.model import PluginModelManager
 
 logger = logging.getLogger(__name__)
@@ -280,7 +281,9 @@ class LargeLanguageModel(AIModel):
                     callbacks=callbacks,
                 )
 
-                assistant_message.content += chunk.delta.message.content
+                text = convert_llm_result_chunk_to_str(chunk.delta.message.content)
+                current_content = cast(str, assistant_message.content)
+                assistant_message.content = current_content + text
                 real_model = chunk.model
                 if chunk.delta.usage:
                     usage = chunk.delta.usage

api/core/model_runtime/utils/helper.py

@@ -1,6 +1,8 @@
 import pydantic
 from pydantic import BaseModel
 
+from core.model_runtime.entities.message_entities import PromptMessageContentUnionTypes
+
 
 def dump_model(model: BaseModel) -> dict:
     if hasattr(pydantic, "model_dump"):
@@ -8,3 +10,18 @@ def dump_model(model: BaseModel) -> dict:
         return pydantic.model_dump(model)  # type: ignore
     else:
         return model.model_dump()
+
+
+def convert_llm_result_chunk_to_str(content: None | str | list[PromptMessageContentUnionTypes]) -> str:
+    if content is None:
+        message_text = ""
+    elif isinstance(content, str):
+        message_text = content
+    elif isinstance(content, list):
+        # Assuming the list contains PromptMessageContent objects with a "data" attribute
+        message_text = "".join(
+            item.data if hasattr(item, "data") and isinstance(item.data, str) else str(item) for item in content
+        )
+    else:
+        message_text = str(content)
+    return message_text